Police say Ross was an innocent bystander caught up in what they believe was gang-related gunfire.
"It is important for the County of Los Angeles to display an unwavering stance against random acts of violence," said county Supervisor Don Knabe, who requested the reward. "In order to bring this suspect to justice, and demonstrate our intolerance to such heinous crimes, I believe this reward should be established, hoping someone will come forward so that we can bring this suspect to justice."
Investigators say there was an argument between two groups of people and shots were fired into a crowd. Witnesses, including the Wilson coach, heard five to seven shots as the crowd left the stadium after Polytechnic beat Wilson, 34-15.
In addition to Ross, two men, ages 18 and 20, were also shot. They are expected to recover.
A fund has been established to help Ross's family with funeral costs.
Donations to the family should be made out to "Long Beach Education Foundation Melody Ross Memorial Trust Account No. 33-0357679; and checks should be mailed to the Long Beach Education Foundation, c/o Judy Seal, 1515 Hughes Way, Long Beach, CA 90810.
Police urged anyone who took photos or video at the game, and anyone with more information about the crime, to contact detectives Scott Lasch or Malcolm Evans at (562) 570-7244.